Electronic equipment, and more particularly computers, have a backplane constituting a "mother" board for bringing in electrical power and distributing the power to a plurality of stacked printed circuit boards constituting "daughter" boards having the logic circuitry thereon.
In the prior art, the backplane bussing arrangements rely upon copper bus bars deposited thereon. These bus bars have a fixed cross section and are sized to carry the maximum electrical current present anywhere in the bar. These bars are rigid and therefore require fixed straight paths, and the bars are bolted to the printed circuit ("PC") board in order to facilitate the entry of current into the PC board.
An example of the prior art is illustrated in U.S. Pat. No. 4,241,381 issued to Cobaugh et al., and assigned to the assignee of the present invention. In this '381 patent, the PC board is first defined, and then the designer decides where the current should be fed into the PC board. Thereafter, a coordinated grid constituting a rigid structure is laid down (by photo-etching or other depositing means) to overlay each hole in the PC board with a given tolerance therein. The grid must be sized for the total current going into the PC board (for the required circular mil area or ("CMA") and thus the same ("massive") amount of copper is used everywhere. After soldering, holes are drilled into the rigid grid structure to coincide with the plurality of holes in the PC board, thus requiring that the respective holes be located at relatively "tight" tolerances during the manufacturing operations. Bolts are run through the aligned holes, and the bolts are tightened to the desired torque.
The bolted connections often become loose after the equipment has been operated out in the field, owing to a number of environmental factors, and internal losses due to increased resistance are encountered in the system. With these systems, changes in the electrical resistance (even in the micro-ohm range) can equate into significant losses and result in erratic operation of the logic circuitry in the equipment. Accordingly, periodic re-tightening or re-torquing of the bolts is required, and this is an annoying service problem.
Additional prior art is listed herein as follows:
______________________________________ Inventor(s) Pat. No. ______________________________________ Pond et al. 3,368,117 Lynch 3,701,078 Johnson 3,725,843 Douty et al. 4,405,189 Richard et al. 4,472,764 Great Britain 2110-463-B ______________________________________
In Pond et al. '117, a voltage distribution system is disclosed, wherein the bus bar runs only from the power supply. Only a single bend of the bus bar is employed, and the bend is external to the board. Thus there is no flexibility provided for multiple bus bars directly on the board.
In Lynch '078, a holder is disclosed which operates simultaneously as a bussing connector for discrete electrical circuit paths on opposed sides of a substrate. This is not a power distribution system, however.
Johnson '843 discloses bussing connections for printed circuit connectors. However, the bussing is always above the board, never below the board, and the bussing is never bent or twisted; thus insufficient flexibility is provided.
Douty et al. '189 discloses a power distribution block for supplying bussed power to a circuit board, but merely discloses a high-current contact and not a system of flexible busses for adjacent PC boards.
Richard et al. '764 has a terminal block for PC boards and merely discloses a plurality of parallel bus bars without inherent flexibility to accommodate a plurality of configurations.
Great Britain '463-B discloses a flexible bar with a capacitor therebetween.
While these prior art teachings are interesting, nevertheless they have certain disadvantages or deficiencies which detract from their utility and flexibility; and thus their teachings are not adaptable to an improved system for distributing power to a plurality of PC boards.